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Month: August 2009

Rats fed a high-fat diet show a stark reduction in their physical endurance and a decline in their cognitive ability after just nine days, a study by Oxford University researchers has shown.

The research, funded by the British Heart Foundation and published in the FASEB Journal, may have implications not only for those eating lots of high-fat foods, but also athletes looking for the optimal diet for training and patients with metabolic disorders.

‘We found that rats, when switched to a high-fat diet from their standard low-fat feed, showed a surprisingly quick reduction in their physical performance,’ says Dr Andrew Murray, who led the work at Oxford University and has now moved to the University of Cambridge. ‘After just nine days, they were only able to run 50 per cent as far on a treadmill as those that remained on the low-fat feed.’

High-fat diets, such as those that are prevalent in Western countries, are known to be harmful in the long term and can lead to problems such as obesity, diabetes and heart failure. They are also known to be associated with a decline in cognitive ability over long time spans. But little attention has been paid to the effect of high-fat diets in the short term.

Physical endurance – how long we can keep exercising – depends on how much oxygen can be supplied to our muscles and how efficiently our muscles release energy by burning up the fuel we get from the food we eat. In particular, using fat as a fuel is less efficient than using glucose from carbohydrates, but the metabolic changes induced by different diets are complex and it has been controversial whether high-fat feeding for a short time would increase or decrease physical performance.

The Oxford team set out to investigate whether rats fed a high-fat diet for just a few days showed any change in their physical and cognitive abilities.

All 42 rats were initially fed a standard feed with a low fat content of 7.5 per cent. Their physical endurance was measured by how long they could run on a treadmill and their short-term or ‘working’ memory was measured in a maze task. Half of the rats were then switched to a high-fat diet where 55 per cent of the calories came from fat. After four days of getting used to the new diet, the endurance and cognitive performance of the rats on the low- and high-fat diets was compared for another five days.

‘With the standard feed, 7.5 per cent of the calories come from fat. That’s a pretty low-fat diet, much like humans eating nothing but muesli,’ says Dr Murray. ‘The high-fat diet, in which 55 per cent of the calories came from fat, sounds high but it’s actually not extraordinarily high by human standards. A junk food diet would come close to that.

‘Some high-fat, low-carb diets for weight loss can even have fat contents as high as 60 per cent. However, it’s not clear how many direct conclusions can be drawn from our work for these diets, as the high-fat diet we used was not particularly low in carbs,’ he adds.

On the fifth day of the high-fat diet (the first day back on the treadmill), the rats were already running 30 per cent less far than those remaining on the low-fat diet. By the ninth day, the last of the experiment, they were running 50 per cent less far.

The rats on the high-fat diet were also making mistakes sooner in the maze task, suggesting that their cognitive abilities were also being affected by their diet. The number of correct decisions before making a mistake dropped from over six to an average of 5 to 5.5.

The researchers also investigated what metabolic changes the high-fat diet was inducing in the rats. They found increased levels of a specific protein called the ‘uncoupling protein’ in the muscle and heart cells of rats on the high-fat diet. This protein ‘uncouples’ the process of burning food stuffs for energy in the cells, reducing the efficiency of the heart and muscles. This could at least partly explain the reduction in treadmill running seen in the rats.

The rats that were fed a high fat diet and had to run on the treadmill also had a significantly bigger heart after nine days, suggesting the heart had to increase in size to pump more blood around the body and get more oxygen to the muscles.

While this research has been done in rats, the Oxford team and Andrew Murray’s new group in Cambridge are now carrying out similar studies in humans, looking at the effect of a short term high-fat diet on exercise and cognitive ability.

The results will be important not only in informing athletes of the best diets to help their training routine, but also in developing ideal diets for patients with metabolic disorders such as diabetes, insulin resistance or obesity. People with such conditions can have high levels of fat in the blood and show poor exercise tolerance, some cognitive decline, and can even develop dementia over time.

‘These are startling results,’ says Professor Kieran Clarke, head of the research team at Oxford University. ‘It shows that high-fat feeding even over short periods of time can markedly affect gene expression, metabolism and physical performance. By optimising diets appropriately we should be able to increase athletes’ endurance and help patients with metabolic abnormalities improve their ability to exercise and do more.’

‘In little more than a week, a change in diet appears to have made the rats’ hearts much less efficient,’ says Professor Jeremy Pearson, Associate Medical Director of the British Heart Foundation, who funded the research. ‘We look forward to the results of the equivalent studies in human volunteers, which should tell us more about the short-term effects of high-fat foods on our hearts. We already know that to protect our heart health in the long-term, we should cut down on foods high in saturated fat.’

Experts estimate that over 24 million people worldwide suffer from dementia, and many of these people live in low- and middle-income countries. Recently, there has been growing interest in whether dietary factors, particularly oily fish and meat, might influence the onset and/or severity of dementia. Oily fish are rich in omega-3 long-chain polyunsaturated fatty acids, which some studies suggest are positively related to cognitive function in later life.

Conversely, there is a suggestion from some studies that increased meat consumption may be related to cognitive decline. To examine this, a group of international researchers studied older people in 7 middle- to low-income countries. You can read the results of their study in the August 2009 issue of the American Journal of Clinical Nutrition.

Data from 14,960 participants (≥65 y of age) living in China, India, Cuba, the Dominican Republic, Venezuela, Mexico, and Peru were analyzed. Dietary habits were assessed by using standard, culturally appropriate face-to-face interviews, and dementia was diagnosed by using validated culturally and educationally fair criteria.

In each of the study countries, except India, there was an inverse association between fish consumption and dementia prevalence. These data extend to low- and middle-income countries previous conclusions from industrialized countries that increased fish consumption is associated with lower dementia prevalence in later life.

The authors propose that this relation is not due to poor overall nutritional status in those with dementia, because meat consumption tended to be higher in this group. The relation between meat consumption and dementia remains unclear.

Two hundred million Americans are overweight and 100 million are obese. In the UK, approximately 24 million people are overweight and 13.5 million are obese.

Being severely obese is as hazardous to health as smoking. In the US, obesity has now overtaken smoking as the no. 1 cause of premature death.

More than 75 million Americans have high blood pressure and 24 million people are diabetic. In the UK, 12 million people have high blood pressure and an estimated 3 million people are diabetic. Heart disease remains the no. 1 cause of death for men and women, followed by stroke and obesity-related cancers.

In the US, 60 percent of bankruptcies are caused by what has become known as “medical debt”.

Fast food, fast medicine, fast news and fast lives have turned many of us into sick, uninformed, indebted, “processed” people.

A new documentary called Processed People features interviews from nine health and environmental experts/advocates. They discuss how and why we have got into this mess and what we can do to break the “processed people” cycle.

If you would like to escape from the “processed people” cycle and live as nature intended, please come and learn how to cook with natural unprocessed foods at Cooking for Health classes, held throughout the year in Somerset, UK.

A study by Exeter University in the UK, published in the Journal of Applied Physiology, reveals that drinking beetroot juice reduces oxygen uptake to an extent that cannot be achieved by any other known means, including training.

The research team believes that the findings could be of great interest to endurance athletes. They could also be relevant for elderly people or those with cardiovascular, respiratory or metabolic diseases.

The research team conducted their study with eight men aged between 19 and 38. They were given 500 ml per day of organic beetroot juice for six consecutive days before completing a series of tests, involving cycling on an exercise bike. On another occasion, they were given a placebo of blackcurrant cordial for six consecutive days before completing the same cycling tests.

After drinking beetroot juice the group was able to cycle for an average of 11.25 minutes, which is 92 seconds longer than when they were given the placebo. This would translate to a 2 per cent reduction in the time taken to cover a set distance. The group that had consumed the beetroot juice also had lower resting blood pressure.

The researchers are not yet sure of the exact mechanism that causes the nitrate in the beetroot juice to boost stamina. However, they suspect it could be a result of the nitrate turning into nitric oxide in the body, reducing the oxygen cost of exercise.

They now hope to conduct further studies to look in more detail at the effects of nitrate-rich foods on exercise physiology.

Corresponding author of the study, Professor Andy Jones of the University of Exeter’s School of Sport and Health Sciences, said:

“Our study is the first to show that nitrate-rich food can increase exercise endurance. We were amazed by the effects of beetroot juice on oxygen uptake because these effects cannot be achieved by any other known means, including training. I am sure professional and amateur athletes will be interested in the results of this research. I am also keen to explore the relevance of the findings to those people who suffer from poor fitness and may be able to use dietary supplements to help them go about their daily lives.”

This study follows research by Barts and the London School of Medicine and the Peninsula Medical School (published in February 2008 in the American Heart Association journal Hypertension), which found that beetroot juice reduces blood pressure.

This study was well-designed and well-reported. It is, however, important to note that due to its small size and the short-term physiological measurements taken, it does not provide unequivocal evidence that beetroot improves stamina and further research is needed.

Researchers examined dietary amino acids, the building blocks of protein, and their effect on blood pressure.

Glutamic acid is the most common amino acid and accounts for almost a quarter (23 percent) of the protein in vegetable protein and almost one fifth (18 percent) of animal protein.

They found that a 4.72 percent higher dietary intake of the amino acid glutamic acid as a percent of total dietary protein correlated with lower group average systolic blood pressure, lower by 1.5 to 3.0 millimeters of mercury (mm Hg). Group average diastolic blood pressure was lower by 1.0 to 1.6 mm Hg.

Systolic blood pressure is the force when the heart beats; diastolic pressure is the pressure when the heart rests between beats.

This average lower blood pressure seems small from an individual perspective. But, on a population scale, it represents a potentially important reduction, said Jeremiah Stamler, M.D., lead author of the study.

“It is estimated that reducing a population’s average systolic blood pressure by 2 mm Hg could cut stroke death rates by 6 percent and reduce mortality from coronary heart disease by 4 percent,”

said Stamler, Professor Emeritus of the Department of Preventive Medicine in the Feinberg School of Medicine at Northwestern University in Chicago, Ill.

Based on American Heart Association 2009 statistics, 6 percent of stroke deaths would be more than 8,600 people and four percent of coronary heart deaths represents about 17,800 lives saved per year.

“High blood pressure is a major cardiovascular disease risk factor, and blood pressure tends to rise with age starting early in life so that the majority of the U.S. population age 35 and older is affected by pre-hypertension or hypertension,” he said. “We have a massive public health problem, and trying to address it by the strategy that has prevailed for years — diagnosis and drug treatment — is inadequate. While clinically useful, it fails as a long-term approach for ending this massive problem.”

The only long-term approach is to prevent pre-hypertension and hypertension by improved lifestyle behaviours, Stamler said. This includes maintaining a healthy body weight, having a fruit and vegetable-rich eating pattern and participating in regular physical activity.

Researchers analyzed data from the International Study on Macro/Micronutrients and Blood Pressure (INTERMAP), on 4,680 people ages 40-59 in 17 rural and urban populations in China, Japan, the United Kingdom and the United States. INTERMAP is a basic population study aiming to clarify the role of multiple nutrients in the etiology of unfavourable blood pressure patterns prevailing for most middle-aged and older individuals. Stamler and colleagues analyzed data from eight blood pressure tests, four diet recall surveys and two 24-hour urine collections for each participant.

“Although our research group and others earlier reported an association between higher consumption of vegetable protein and lower blood pressure, as far as we know this is the first paper on the relation of glutamic acid intake to blood pressure,”

said Ian J. Brown, Ph.D., co-author of the study and a research associate in the Department of Epidemiology and Public Health at Imperial College London.

Common sources of vegetable protein include beans, whole grains — including whole grain rice, pasta, breads and cereals — and soy products such as tofu. Durum wheat, which is used to make pasta, is also a good source of vegetable protein.

Stamler noted that there are no data on the possible effects of glutamic acid supplements and emphasized the importance of “improved habitual food intake for the prevention and control of hypertension, not popping pills.”

To learn how to cook with vegetable proteins and other whole foods, why not come along to a Cooking for Health course, held throughout the year in Somerset, UK.